Electronic thermometers are widely used in the healthcare field for measuring a patient's body temperature. A typical electronic thermometer includes a sensor probe having an elongated shaft portion and a tip portion. The tip portion contains electronic temperature sensors, such as thermistors or other temperature-sensitive elements. Often, a covering (e.g., aluminum cap) for the tip portion makes thermal contact with the temperature sensitive elements contained within the tip portion. When the tip of the probe is placed, for example, in a patient's mouth, the patient's body heats the tip and the temperature sensor components sense the temperature of the tip.
A base unit typically houses additional electronic components for the thermometer. These components may be connected to the electronic temperature sensor components in the probe shaft by wires or the like. In some instances, a handle portion of the probe shaft contains electronics in addition to or instead of the base unit. The electronic components receive input from the temperature sensor components for generating an output representative of the patient's temperature. The thermometer usually displays this output to a user. Additional features of known electronic thermometers include audible temperature level notifications such as beeps or tone alert signals. A disposable cover or sheath is typically fitted over the shaft portion and disposed after each use of the thermometer for sanitary reasons.
The construction of the probe is important for ensuring accurate temperature measurements and repeatability during manufacturing. One known probe construction mounts the electronic components (e.g., the temperature sensitive elements) on a flexible substrate that supports and provides electrical connection for the components. The combination of the components and the flexible substrate is commonly called a “flex circuit”. The substrate may be initially flat to facilitate ease of mounting the components, but can be bent into position upon assembly into the probe. For example, the flexible substrate may be bent to place a thermistor in position for contacting the probe tip covering. The components can be glued in place with a thermally conductive adhesive in the final assembly. However, before the adhesive is brought into contact with the components and/or before the adhesive sets, the components may undesirably move. The result of motion can be insufficient contact of the components with the tip and/or other parts of the probe to heat or sense temperature in the final assembly. Likewise, the components may be positioned incorrectly or with an unacceptable level of variability from one thermometer to another.